Analysis of packer forces in vertical wells and frictionless sail sections

Abstract

New discoveries could represent challenges in many ways such as high pressures and high temperatures. The reservoir contains corrosive liquids that are being produced to the surface. Since the casing is expensive to replace, it is common practice to flow the reservoir fluid through a protective tubing. Also the tubing and packer are part of the primary well barrier. Change of temperature and pressure can make the tubing buckle. When wells need intervention, for instance to repair some type of damage or to increase the production, intervention equipment run through the tubing could get stuck in the buckled section. This thesis will study buckling of tubing in vertical wells and sail sections for frictionless wells. By using theory, theoretical field cases and reverse engineering this thesis reveals the equations used by the buckling simulation software called WellCat 2003.0.4.0 from Landmark. The fictitious force, also known as the buckling force, is discussed in details. The buckling limit used by WellCat is found, showing that the simulator performs very conservative buckling calculations. Buckling is less severe in sail sections than in vertical sections. The effect of inclination of the sail section on the piston effect, helical buckling length change and ballooning effect is shown for a mechanical set packer.